Testing Deploy Functions Using Sinon.JS in Yaydoc

In yaydoc, we deploy the generated documentation to the GitHub pages as well as Heroku. It is one of the important functions in the source code. I don’t want to break the build in future by any unnoticed change, so I decided to write a test case for deploy function. But the deploy function had lot dependencies like child processes, sockets, etc. Also it is not a pure function, so there is no return object to assert the value. Then I decided to stub for child process to check whether the correct script was passed or not. In order to write stub I decided to use sinon js framework because it can be used for writing stubs, mocks and spies. One of the advantages with sinon is that it’ll work with any testing framework.

sinon.stub(require("child_process"), "spawn").callsFake(function (fileName, args) {
  if (fileName !== "./ghpages_deploy.sh" ) {
    throw new Error(`invalid ${fileName} invoked`);

  if (fileName === "./ghpages_deploy.sh") {
    let ghArgs = ["-e", "-i", "-n", "-o", "-r"];
    ghArgs.forEach(function (x)  {
      if (args.indexOf(x) < 0) {
        throw new Error(`${x} argument is not passed`);
  let process = {
    on: function (listenerId, callback) {
      if (listenerId !== "exit") {
        throw new Error("listener id is not exit");
  return process;

In sinon you can create s stub by passing the object in the first parameter and the method name in the second parameter to sinon’s stub method. After it returns an object, pass the function which you would like to replace with the “callFakes” function.

In above code, I wrote a simple stub which overwrites NodeJS child_process’s spawn method. So I passed the “child_process” module in the first parameter and “spawn” method name in the second parameter. You must check whether they are passing the correct deploy script and the correct parameter. So, I wrote a function which checks the condition and then pass the method to the callFakes method.

describe('deploy script', function() {
  it("gh-pages deploy", function() {
    deploy.deployPages(fakeSocket, {
      gitURL: "https://github.com/sch00lb0y/yaydoc.git",
      encryptedToken: crypter.encrypt("dummykey"),
      email: "admin@fossasia.org",
      uniqueId: "ajshdahsdh",
      username: "fossasia"

Finally test the deploy function by calling it. I use mocha as a testing framework. I have already written a blog on mocha. If you’re interested in mocha please check out this blog.


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Testing child process using Mocha in Yaydoc

Mocha is a javascript testing framework. It can be used in both nodeJS and browser as well, also it is one of the most popular testing framework available out there. Mocha is widely used for the Behavior Driven Development (BDD). In yaydoc, we are using mocha to test our web UI. One of the main task in yaydoc is documentation generation. We build a bash script to do our documentation generation. We run the bash script using node’s child_process module, but then in order to run the test you have to execute the child process before test execution. This can be achieved by mochas’s before hook. Install mocha in to your system

npm install -g mocha

Here is the test case which i wrote in yaydoc test file.

const assert = require('assert')
const spawn = require('child_process').spawn
const uuidV4 = require("uuid/v4")
describe('WebUi Generator', () => {
  let uniqueId = uuidV4()
  let email = 'fossasia@gmail.com'
  let args = [
    "-g", "https://github.com/fossasia/yaydoc.git",
    "-t", "alabaster",
    "-m", email,
    "-u", uniqueId,
    "-w", "true"
  let exitCode

  before((done) => {
    let process = spawn('./generate.sh', args)
    process.on('exit', (code) => {
      exitCode = code
  it('exit code should be zero', () => {
    assert.equal(exitCode, 0)

Describe() function is used to describe our test case. In our scenario we’re testing the generate script so we write as webui generator. As I mentioned above we have to run our child_process in before hook. It() function is the place where we write our test case. If the test case fails, an error will be thrown. We use the assert module from mocha to do the assertion. You can see our assertion in first it()  block for checking exit code is zero or not.

mocha test.js --timeout 1500000

Since documentation takes time so we have to mention time out while running mocha. If your test case passes successfully, you will get output similar to this.

WebUi Generator
    ✓ exit code should be zero



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